An open circuit is when the gap between the two pieces of conducting material prevents the electric charges from traveling through the circuit. A closed circuit is when the two pieces of conducting material touch, which allows the electric charge to flow through the circuit.

Electrons are negatively charged, so they are attracted to the positive end of a battery and repelled by the negative end. So when the battery is hooked up to something that lets the electrons flow through it, they flow from negative to positive.

A circuit is always a loop, it is always a closed path, an electric circuit is a complete path with electric flows.